As a conventional technology of this sort, there is one disclosed in Patent Document 1. Disclosed in this Patent Document 1 are an NOx reduction system, which includes an upstream-side, first aftertreatment device for collecting particulates contained as suspended particulate matter in exhaust gas from an engine, that is, a PM collection filter and also a downstream-side, second aftertreatment device for purifying and detoxifying nitrogen oxide (NOx), that is, a reduction catalyst, and also a construction that the PM collection filter and the reduction catalyst are arranged in a turned square “U” pattern via a piping which forms an exhaust passage of the engine.
Mounting of such an NOx reduction system is also desired in a construction machine. The above-mentioned conventional technology disclosed in the Patent Document 1 will hereinafter be described with respect to a mounting structure for the NOx reduction system, which can be contemplated upon mounting the NOx reduction system on a construction machine, for example, a hydraulic excavator.
FIG. 5 is a plan view showing certain essential parts of the conventionally-contemplated mounting structure for the NOx reduction system for the construction machine, and FIG. 6 is a view as seen in the direction of arrow B in FIG. 5.
As shown in these FIGS. 5 and 6, the hydraulic excavator is provided with a revolving upperstructure 40 mounted on a travel base. This revolving upperstructure 40 is provided with an engine compartment 41 and a counterweight 42 arranged adjacent the engine compartment 41 at a rear position of a body to maintain stability of the body. An engine 43 and a hydraulic pump 44 drivable by the engine 43 are arranged in the engine compartment 41. Upon application of the above-mentioned conventional technology disclosed in the Patent Document 1 to such a hydraulic excavator, it may be possible to contemplate a construction that as shown in FIG. 5, a PM collection filter 46 and a reduction catalyst 48 are arranged side by side in a lateral direction of the construction machine such that the reduction catalyst 48 is located on an outboard side, the engine 43 is communicated to the PM collection filter 46 via a piping 45, the PM collection filter 46 is communicated to the reduction catalyst 48 via a piping 47, and a muffler 49 is arranged at a part of the reduction catalyst 48 to release exhaust gas into the atmosphere. Specifically, it may be possible to contemplate a construction that the PM collection filter 46 and the reduction catalyst 48 are arranged via the piping 47 in a turned square “U” pattern as seen in plan.
Patent Document 1: JP-A-2005-155404